The transverse and longitudinal sizes of crystallites in thermoreversible polyethylene gels and xerogels were measured using wide-angle X-ray scattering and a low-frequency Raman spectroscopy, and were found to be 10-40 and 4-5 nm, respectively. The experimental data evidence the imperfection of primary crystallites in both dimensions. The gel-to-solid transition results in gaining the direct interaction between crystalline entities with increasing the cracking, on the one hand, and forming the clusters of stacked crystalline platelets linked with regular molecular rods, on the other hand. These contact interaction leads, in addition, to the coiling of a great part of regular sequences that emanate from the crystallite cores to the amorphous region. (C) 2003 Wiley Periodicals, Inc.